Final answer:
During pregnancy, the relationship between blood volume and cardiac index (C.I.) is that as blood volume increases, cardiac output and the cardiac index also increase.
Step-by-step explanation:
During pregnancy, blood volume increases by approximately 30 percent, which helps manage the demands of fetal nourishment and waste removal. This increased blood volume also causes a moderate rise in pulse and blood pressure. The relationship between blood volume and cardiac index (C.I.) in pregnant women is that as blood volume increases, cardiac output also increases, leading to an elevated cardiac index.